Beam shaping device for shaping the cross-section of a light beam and system for launching into an optical fiber a light beam having an elongated cross-section and being emitted by an elongated laser beam source

ABSTRACT

The invention relates to a beam shaping device for shaping the cross-section of a light beam, comprising at least one beam shaping unit with beam splitting means, beam deflecting means, and beam combination means. The beam splitting means are capable of diving up a light beam that is incident on the beam shaping unit into two partial beams. The beam deflecting means are capable of deflecting at least one of the partial beams onto the beam combination means and said beam combination means are capable of combining the two partial beams in such a manner that the cross-section of the light beam exiting the beam shaping unit is reduced in size in a first direction compared to the cross-section of the light beam that is incident on the beam shaping unit and is increased in size in a second direction perpendicular thereto. the invention is further characterized in that the beam combination means can also be used as beam splitting means, whereby only one of the partial beams is deflected by the beam deflecting means, while the other partial beam is directly incident on the beam combination means.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a beam shaping device for shaping thecross section of a light beam comprising at least one beam shaping unitwith beam division means, beam deflection means and beam combinationmeans, the beam division means being able to divide a light beamincident on the beam shaping unit into two component beams, the beamdeflection means being able to deflect at least one of the componentbeams to the beam combination means, and the beam combination meansbeing able to combine the two component beams, such that the crosssection of the light beam emerging from the beam shaping unit comparedto the cross section of the light beam entering the beam shaping unit isreduced in the first direction and is enlarged in a second directionwhich is perpendicular to it. Furthermore, this invention relates to anarrangement for injecting a light beam with an elongated cross sectionproceeding from an elongated laser light source into an optical fiber,comprising a laser light source, a collimation unit which is locatedbehind it in the beam direction, a beam shaping device of theaforementioned type and a focussing unit which is located behind thebeam shaping device and which can focus the beam incident on it onto theoptical fiber.

[0002] A beam shaping device of the aforementioned type and anarrangement of the aforementioned type are known from German patent DE195 37 265 C1. In the embodiment of a beam shaping unit described in ita rhomboid prism pair which separates the incident radiation into twocomponent beam bundles is used as the beam division means. The beamdeflection means are two half cubic prisms which are integrated into thecorresponding component beam paths, as a result of the relatively longpath of the component beam bundle which has been traversed in this beamshaping unit there being a lens located between the rhomboid prism pairand the half cube prism. The beam combination means is a fifth prismwhich deflects the component beam bundles which are incident on it andcombines them again.

[0003] The disadvantage in this beam shaping unit is that overall sevencomponents are used, each of the individual component beams passingthrough eight optionally partially absorbing surfaces of opticalcomponents and being reflected each on two other surfaces of theaforementioned components, which surfaces may not be 100% reflective.Based on the many surfaces which must be transmitted or on whichreflection must take place, a relatively great cost must be borne tocoat the surfaces accordingly with respect to transmission orreflection. In particular, when several of these beam shaping units areset up in succession, such a beam shaping device will be less effective.Furthermore, as a result of the many components used and as a result ofthe high coating cost these beam shaping units will be extremelyexpensive.

[0004] An arrangement of the initially mentioned type is generally usedwhenever for example laser radiation proceeding for example from a laserdiode bar is to be focussed on an optical fiber. In particular, as aresult of the almost line-shaped laser light source with individualemission centers which are located spaced apart over the length of theline and the different divergences in the slow axis and fast axisdirection, it is a good idea to use a beam shaping device of theinitially mentioned type in order to repeatedly shape and combine thelaser light emerging from the laser diode bar with an almost line-shapedcross section, so that a laser beam bundle with an almost square crosssection is formed which then can be focussed more easily on the opticalfiber. The effectiveness and economic efficiency of such an arrangementof course follow from the effectiveness and economic efficiency of thebeam shaping device used in it.

[0005] One object of this invention is to devise a beam shaping deviceof the initially mentioned type and an arrangement of the initiallymentioned type which are built efficiently and economically.

SUMMARY OF THE INVENTION

[0006] The beam combination means are also used as beam division means,only one of the component beams being deflected by the beam deflectionmeans, conversely the other component beam being directly incident onthe beam combination means. This measure drastically reduces the numberof transmissions or reflections of the individual component beams.Furthermore, a beam shaping unit as claimed in the invention in theideal case can consist of two individual optical components, converselyin the prior art for the same function seven components being necessary.In particular, one of the component beams will be incident directly onthe beam combination means without prior passage through other opticalcomponents so that for this component beam the number of transmissionsor reflections is minimized. Advantageously the second of the componentbeams for dividing the beam will run unhindered past the component whichis being used as the beam combination means and the beam division meansand will be deflected by the beam deflection means onto the functionalsections of the component which is used as the beam combination meansand the beam division means, which sections are used as beam combinationmeans. This measure also minimizes the number of transmissions andreflections of the second component beam.

[0007] Advantageously the beam combination means comprise two specularsurfaces which include an angle to one another, and each of thecomponent beams which are to be combined by the beam combination meanscan be reflected on one of the specular surfaces. Especially for thecase in which the specular surfaces are the outside surfaces of the beamcombination means, each of the component beams will undergo only onereflection on this component, but not an additional transmission.

[0008] According to one preferred embodiment of this invention, there isa single prism as the beam combination means and at the same time thebeam division means, the specular surfaces which reflect the componentbeams being made as preferably mirrored surfaces of this prism. Such aprism represents an especially simple but nevertheless very effectiveembodiment of the component which is used at the same time as the beamcombination means and beam division means.

[0009] Advantageously the prism which is used as the beam division meansand as the beam combination means can have a base surface which is madeas an isosceles right triangle, the specular surfaces being those prismsurfaces which each extend between the legs of the base surfaces so thatthe specular surfaces include an angle of 90° with one another. Bychoosing one such right-angled prism the desired beam combinationfunction can be implemented most easily, in which specifically the twospecular surfaces which are at an angle of 90° to one another are eachaligned at an angle of 45° or −45° to the component beams which run fromthe opposite directions onto the prism.

[0010] Here the prism which is used as the beam division means or as thebeam combination means can be located in the beam shaping unit such thatthe light beam which is incident on the beam shaping unit and which isto be shaped is cut in half in the first direction which is essentiallyperpendicular to the direction of propagation of the light beam, suchthat one of the two component beams which is formed by this halving runspast the prism onto the beam deflection means and the other of the twocomponent beams which is formed by this halving is directly incident onthe first of the two specular surfaces and is reflected by them in thedirection of the light beam leaving the beam shaping unit. By thiscutting of the beams in half on the prism the first of the two componentbeams in the entire beam shaping unit will ultimately undergo only onereflection on the first of the two specular surfaces and nottransmission. The other of the component beams according to the choiceof the beam deflection means will undergo two to four reflections ortransmissions on the beam deflection means and exactly one reflection onthe second specular surface, but an additional transmission neither onthe beam division means nor on the beam combination means. In this waythe number of transmissions and reflections is minimized with asimultaneous extremely economical structure of the beam shaping deviceas claimed in the invention.

[0011] Preferably the prism which is used as the beam division means oras the beam combination means is located in the beam shaping unit suchthat a light beam which is incident on the beam shaping unit runsparallel to the prism surface which connects to one another the twoprism surfaces which are made as specular surfaces. This ensures thatwith the corresponding calibration of the light beam which is to beshaped exactly one half of the beam is incident on the first mirrorsurface and the other half of the beam runs past the prism in thedirection to the beam deflection means and now parts of the beam are notabsorbed or reflected away in an uncontrolled manner on any additionaledges or the like.

[0012] Here it can be provided that the component beam which runs pastthe prism which is being used as the beam division means or beamcombination means is incident on the beam deflection means in thepropagation direction behind the prism; the beam deflection meansdeflect the component beam such that it is incident on the second of thespecular surfaces in the direction which is opposite the propagationdirection and is reflected by these surfaces in the direction of thelight beam which is leaving the beam shaping unit. In this way thestructure of the beam shaping device or beam shaping unit as claimed inthe invention is relatively compact.

[0013] According to one preferred embodiment of this invention, the beamdeflection means are made as an imaging unit and cause 1:1 imaging ofthe component beam which is incident on it onto the second specularsurface. This imaging results in that the two component beams can beoptimally combined by the beam combination means because especially nodivergence or hardly any different divergence can occur between the twocomponent beams.

[0014] Preferably the imaging unit here can have essentially the shapeof a planoconvex lens, and the component beam can enter the imaging unitthrough the convex lens surfaces, can be reflected on the plane surfacewhich is preferably mirrored and can emerge from the convex lens surfacein the direction to the second specular surface of the beam combinationmeans. In this way deflection and the associated 1:1 imaging isaccomplished by two transmissions and one reflection so that overallvery effective shaping of the beam cross section occurs.

[0015] According to another embodiment of this invention, the beamdeflection means is made as a prism, and the component beam which isincident on the prism can be deflected by it in the direction which isopposite the propagation direction onto the second specular surface ofthe beam combination means. The choice of a prism as the beam deflectionmeans is an especially good idea for very extended beam cross sectionsbecause by inserting a prism into the beam path no additional imagingerrors can occur, as would be the case in a lens or the like.

[0016] Here the prism which is used as a deflection means can likewisehave a base surface which is made as an isosceles right triangle, thecomponent beam entering the prism passing vertically through the prismsurface which connects the base sides of these triangles to one anotherand on each of the other two prism surfaces being reflected at an angleof essentially 45°, preferably the two prism surfaces on which thecomponent beam is reflected being mirrored. A beam deflection meanswhich is made in this way is characterized by an extremely simple andeconomical structure with high functionality.

[0017] Advantageously, the beam shaping device can have more than onebeam shaping unit, especially three or four beam shaping units which arearranged in succession such that the cross section of the light beam ismade smaller in each of the beam shaping units in the first directionand is enlarged in the second direction which is perpendicular to it.Here the cross section of the light beam emerging from the beam shapingunit or from one of the beam shaping units compared to the cross sectionof the light beam entering the beam shaping unit or one of the beamshaping units can be cut in half in the first direction and can bedoubled in the second direction which is perpendicular to it. Forexample, by connecting four such beam shaping units in succession thelight beam would be compressed by a factor of 16 in the first directionand in the second direction perpendicular to it pulled apart by a factorof 16. Thus such a beam shaping unit is especially suited for theinitially mentioned arrangement for injecting of the laser beam emergingfor example from a laser diode bar into an optical fiber.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other features and advantages of this invention become clearbased on the following description of preferred embodiments withreference to the attached drawings.

[0019]FIG. 1a shows a schematic view of a beam shaping device as claimedin the invention;

[0020]FIG. 1b shows a view of the beam shaping device as shown by arrowIb in FIG. 1a,

[0021]FIG. 1c schematically shows the cross section of the beam which isto be shaped with the beam shaping device;

[0022]FIG. 1d schematically shows the cross section of the beam whichhas been shaped by the beam shaping device;

[0023]FIG. 2a shows a schematic view of another embodiment of a beamshaping device as claimed in the invention;

[0024]FIG. 2b shows a view according to the arrow IIb in FIG. 2a;

[0025]FIG. 3 shows a schematic of another embodiment of a beam shapingdevice as claimed in the invention with a laser light source and a glassfiber and the corresponding focussing lenses; and

[0026]FIG. 4 shows a perspective view of the embodiment as shown in FIG.2.

DETAILED DESCRIPTION OF THE INVENTION

[0027]FIG. 1a and FIG. 1b show a beam shaping device as claimed in theinvention which comprises a beam shaping unit 1 which consists of a beamdivision and beam combination means 2 made as a prism and a beamdeflection means 3 which is made as an imaging unit. The cross section 4of the light beam 5 which is to be shaped by the beam shaping unit 1 isshown in FIG. 1c. The cross section 6 of the light beam 7 which isshaped by the beam shaping unit 1 is shown in FIG. 1d.

[0028]FIG. 1a and FIG. 1b show that the light beam 5 which is incidenton the beam shaping unit 1 has a relatively wide and flat cross section4. The prism is made such that the light beam 5 which is to be shaped isdivided by the prism into two component beams 8 and 9 of the same width.In FIG. 1a the component beam 8 runs past under the prism, converselythe component beam 9 is incident on the side of the prism facing theincident beam 5 which is to be shaped. The prism has two base surfaces11 which are made as isosceles right triangles and three right-angleprism surfaces. Two of these prism surfaces are mirrored and thus formthe specular surfaces 10, 12, by which the component beams 8, 9 can bereflected. The reflecting surfaces 10, 12 are each the connectingsurfaces between the legs of the base surfaces 11 and thus enclose aright angle with one another along the apex line 15.

[0029] The base sides of the base surfaces 11 of the prism extend in thereference system which is given in FIG. 1a and FIG. 1b in theZ-direction so that the specular surface 10 facing the component beam 9is aligned at an angle of 45° to the Y direction so that the componentbeam 9 which runs in the Z direction is deflected by reflection on thereflecting surface 10 in the Y direction.

[0030] The component beam 8 which runs past the lower base surface 11 ofthe prism in FIG. 1a enters the imaging unit which is located in FIG. 1ain the Z direction behind the prism 2. The imaging unit is made in theillustrated embodiment as a spherical or slightly aspherical planoconvexlens, with a front convex lens surface 13 facing the prism and a rearplanar mirrored surface 14 which faces away from the prism. As isapparent from FIG. 1a, the component beam 8 enters the imaging unitthrough the lens surface 13 and is reflected on the mirrored surface 14such that it emerges in the X direction offset in turn from the lenssurface 13 and is incident on the second specular surface 12 of theprism. There the component beam 8 as a result of the orientation of thereflecting surface 12 is deflected up into the Y-direction at an angleof 45° to the vertical or to the Y direction, as is clearly apparentfrom FIG. 1b.

[0031] The imaging unit causes 1:1 imaging of the component beam 8. Inparticular, for this purpose an arrangement is feasible, as shown inFIG. 1a, in which the apex line 15 of the prism is aligned parallel tothe reflecting surface 14 of the imaging unit and the distance of theapex line 15 to the frontmost edge of the lens surface 13 of the imagingunit is equal to the focal length L₂ of the lens surface 13. At the sametime the thickness of the imaging unit, i.e. the distance between thefrontmost point of the lens surface 13 and the mirrored surface 14corresponds to the quantity L₁ which corresponds to the product of L₂and the index of refraction of the medium from which the imaging unit ismade.

[0032]FIG. 2 shows another embodiment of a beam shaping device asclaimed in the invention. In this embodiment a beam shaping unit 16 isused which consists of a beam division and beam combination means 2which is made as a first prism and of a beam deflection means 17 whichis made as a second prism. In FIG. 2a and FIG. 2b the same parts areprovided with the same reference numbers as in FIG. 1. Instead of theimaging unit in FIG. 1, for the beam shaping unit 16 there is a secondprism. This prism is likewise a vertical prism, i.e. a prism with anapex angle of 90°. The prism is oriented such that the base surfaces 18lie in the XZ plane and the apex line 19 is located on the side of thesecond prism facing away from the first prism and is exactly flush withthe border of the first prism in the Z-direction, which border is thelower one in FIG. 2a.

[0033] As is apparent from FIG. 2, the component beam 8 enters thesecond prism through the prism surface which connects the base surfaces18 to one another and is reflected there on the two mirrored prismsurfaces 20, 21 such that it emerges in the direction to the prism fromthe base surface 18 and is reflected equivalently to the component beam9 on the specular surface 12 of the first prism in the Y direction. Theembodiment as shown in FIG. 2 is shown in perspective for illustrationin FIG. 4.

[0034]FIG. 3 shows a beam shaping device which comprises four beamshaping units 22, 23, 24, 25. The beam shaping units 22, 23, 24, 25 areeach identical units which correspond to the beam shaping unit 16 fromFIG. 2. Each of these beam shaping units 22, 23, 24, 25 thus comprises afirst prism and a second prism which form a beam division and beamcombination means 2 and a beam deflection means 17.

[0035] The light emerging from the laser light source 26 which is shownschematically as a point and which is made as a laser diode bar isincident on a first beam shaping unit 22 after passing through acollimation unit 27 which is made as a cylinder lens. In this beamshaping unit the cross section of the light beam is changed according toFIGS. 1c and 1 d. Subsequently, the light beam in succession is incidenton the other beam shaping units 23, 24, 25, where the cross section ofthe light beam is changed accordingly. As a result of the fact that thelight beam is shortened in width in each of the beam shaping units 22,23, 24, 25 by a factor of 2 and is doubled in height, the light beamsafter passing through the fourth beam shaping unit 25 will have a widthwhich has been reduced by a factor of 16 and a height of its crosssection which has been increased by a factor of 16. This is shownschematically in FIG. 3. After emerging from the last beam shaping unit25 the light beam is incident on a focussing unit 28 which is made as anessentially spherical lens and by means of which it can be injected intothe optical fiber 29.

1. (Currently Amended) Beam A beam shaping device for shaping the crosssection (4, 6) of a light beam (5, 7) comprising at least one beamshaping unit (1, 16, 22, 23, 24, 25) with beam division means (2), beamdeflection means (3, 17) and beam combination means (2), the beamdivision means (2) being able to divide a light beam (5) which isincident on the beam shaping unit (1, 16, 22, 23, 24, 25) into twocomponent beams (8, 9), the beam deflection means (3, 17) being able todeflect at least one of the component beams (8, 9) to the beamcombination means (2), and the beam combination means (2) being able tocombine the two component beams (8, 9), such that the cross section (6)of the light beam (7) emerging from the beam shaping unit (1, 16, 22,23, 24, 25) compared to the a cross section (4) of the light beam (5)entering the beam shaping unit (1, 16, 22, 23, 24, 25) is reduced in thefirst direction (X) and is enlarged in a second direction (Y, Z) whichis perpendicular to it, characterized in that wherein the beamcombination means (2) are also used as beam division means (2), only oneof the component beams (8) being deflected by the beam deflection means(2, 17), conversely the other component beam (9) being directly incidenton the beam combination means (2).
 2. (Currently Amended) Beam A beamshaping device as claimed in claim 1, wherein the beam combination means(2) comprise two specular surfaces (10, 12) which include an angle toone another, and each of the component beams (8, 9) which are to becombined by the beam combination means can be reflected on one of thespecular surfaces (10, 12).
 3. (Currently Amended) Beam A beam shapingdevice as claimed in claim 2, wherein there is a single prism as thebeam combination means (2) and at the same time the beam division means(2), the specular surfaces (10, 12) which reflect the component beams(8, 9) being made as preferably mirrored surfaces of this prism. 4.(Currently Amended) Beam A beam shaping device as claimed in claim 3,wherein the prism which is used as the beam division means (2) and asthe beam combination means (2) has a base surface (11) which is made asan isosceles right triangle, the specular surfaces (10, 12) being thoseprism surfaces which each extend between the legs of the base surfaces(11) so that the specular surfaces (10, 12) include an angle of 90° withone another.
 5. (Currently Amended) Beam A beam shaping device asclaimed in one of claims 3 or 4 claim 3, wherein the prism which is usedas the beam division means (2) or as the beam combination means (2) islocated in the beam shaping unit (1, 16, 22, 23, 24, 25) such that thelight beam (5) which is incident on the beam shaping unit (1, 16, 22,23, 24, 25) and which is to be shaped is cut in half in the firstdirection (X) which is essentially perpendicular to the direction ofpropagation (Z) of the light beam (5) such that one of the two componentbeams (8) which is formed by this halving runs past the prism onto thebeam deflection means (3) and the other of the two component beams (9)which is formed by this halving is directly incident on the first of thetwo specular surfaces (10) and is reflected by them in the direction (Y)of the light beam (7) leaving the beam shaping unit (1, 16, 22, 23, 24,25).
 6. (Currently Amended) Beam A beam shaping device as claimed in oneof claims 3 to 5 claim 3, wherein the prism which is used as the beamdivision means (2) or as the beam combination means (2) is located inthe beam shaping unit (1, 16, 22, 23, 24, 25) such that a light beam (5)which is incident on the beam shaping unit (1, 16, 22, 23, 24, 25) runsparallel to the prism surface which connects the two prism surfaceswhich are made as specular surfaces to one another (10, 12). 7.(Currently Amended) Beam A beam shaping device as claimed in one ofclaims 3 to 6 claim 3, wherein the prism which is being used as the beamdivision means (2) or beam combination means (2) is located in the beamshaping unit (1, 16, 22, 23, 24, 25) such that the two specular surfaces(10, 16) include an angle of 45° or −45° with the propagation direction(Z) of the light beam (5) which is to be shaped by the beam shaping unit(1, 16, 22, 23, 24, 25).
 8. (Currently Amended) Beam A beam shapingdevice as claimed in one of claims 5 to 7 claim 5, wherein the componentbeam (8) which runs past the prism which is being used as the beamdivision means (2) or beam combination means (2) is incident on the beamdeflection means (3, 17) in the propagation direction (Z) behind theprism, the beam deflection means deflect the component beam (8) suchthat it is incident on the second of the specular surfaces (12) in thedirection opposite the propagation direction (Z) and is reflected bythese surfaces in the direction (Y) of the light beam (7) which isleaving the beam shaping unit (1, 16, 22, 23, 24, 25).
 9. (CurrentlyAmended) Beam A beam shaping device as claimed in one of claims 1 to 8claim 1, wherein the beam deflection means (3) are made as an imagingunit and cause 1:1 imaging of the component beam (8) which is incidenton it onto the second specular surface (12).
 10. (Currently Amended)Beam A beam shaping device as claimed in claim 9, wherein the imagingunit has essentially the shape of a planoconvex lens, and the componentbeam (8) can enter the imaging unit through the convex lens surface(13), can be reflected on the plane surface (14) which is preferablymirrored and can emerge from the convex lens surface (3) in thedirection to the second specular surface (12) of the beam combinationmeans (2).
 11. (Currently Amended) Beam A beam shaping device as claimedin one of claims 1 to 8 claim 1, wherein the beam deflection means (17)is made as a prism, and the component beam (8) which is incident on theprism can be deflected by it in the direction opposite the propagationdirection (Z) onto the second specular surface (12) of the beamcombination means (2).
 12. (Currently Amended) Beam A beam shapingdevice as claimed in claim 11, wherein the prism which is used as adeflection means (17) likewise has a base surface (18) which is made asan isosceles right triangle, the component beam (8) entering the prismpassing vertically through the prism surface which connects the basesides of these triangles to one another and on each of the other twoprism surfaces (20, 21) is reflected at an angle of essentially 45°,preferably the two prism surfaces (20, 21) on which the component beam(8) is reflected being mirrored.
 13. (Currently Amended) Beam A beamshaping device as claimed in one of claims 1 to 12 claim 1, wherein thebeam shaping device comprises more than one beam shaping unit (22, 23,24, 25), especially three or four beam shaping units (22, 23, 24, 25)which are arranged in succession such that the cross section of thelight beam is made smaller in each of the beam shaping units (22, 23,24, 25) in the first direction and is enlarged in the second directionwhich is perpendicular to it.
 14. (Currently Amended) Beam A beamshaping device as claimed in one of claims 1 to 13 claim 1, wherein thecross section (6) of the light beam (7) emerging from the beam shapingunit (1, 16, 22, 23, 24, 25) or from one of the beam shaping units (1,16, 22, 23, 24, 25) compared to the cross section (4) of the light beamentering the beam shaping unit (1, 16, 22, 23, 24, 25) or one of thebeam shaping units (1, 16, 22, 23, 24, 25) is cut in half in the firstdirection (X) and is doubled in the second direction (XZ) which isperpendicular to it.
 15. (Currently Amended) Arrangement An arrangementfor injecting a light beam (5) with an elongated cross section (4)proceeding from an elongated laser light source (22) into an opticalfiber (29), comprising a laser light source (26), a collimation unit(27) which is located behind it in the beam direction (Z), a beamshaping device with the features of one of claims 1 to 14 claim 1 and afocussing unit (28) which is located behind the beam shaping device andwhich can focus the light beam incident on it onto the optical fiber(29).